EP0072552A2 - Detectable element - Google Patents
Detectable element Download PDFInfo
- Publication number
- EP0072552A2 EP0072552A2 EP82107389A EP82107389A EP0072552A2 EP 0072552 A2 EP0072552 A2 EP 0072552A2 EP 82107389 A EP82107389 A EP 82107389A EP 82107389 A EP82107389 A EP 82107389A EP 0072552 A2 EP0072552 A2 EP 0072552A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- permanent magnet
- detectable element
- capsule
- element according
- magnetic field
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000002775 capsule Substances 0.000 claims abstract description 49
- 239000012790 adhesive layer Substances 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 239000010410 layer Substances 0.000 description 7
- 229910052742 iron Inorganic materials 0.000 description 4
- 230000005389 magnetism Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910001369 Brass Inorganic materials 0.000 description 1
- 241000238366 Cephalopoda Species 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 230000005355 Hall effect Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- ORQBXQOJMQIAOY-UHFFFAOYSA-N nobelium Chemical compound [No] ORQBXQOJMQIAOY-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052573 porcelain Inorganic materials 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
- G08B13/2428—Tag details
- G08B13/2437—Tag layered structure, processes for making layered tags
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/02—Mechanical actuation
- G08B13/14—Mechanical actuation by lifting or attempted removal of hand-portable articles
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
- G08B13/2428—Tag details
- G08B13/2437—Tag layered structure, processes for making layered tags
- G08B13/2442—Tag materials and material properties thereof, e.g. magnetic material details
Definitions
- the present invention relates to a detectable element for enabling a detector to detect the passage or presence of an object to which the detectable element is attached.
- detectable element which comprises a small permanent magnet that can be attached to an object to be detected.
- the magnetic flux emanating from the permanent magnet is detected by a detector so that arrival of the object at the location or passage thereof through the location can be ascertained.
- detectable elements have found a wide variety of applications.
- the detectable elements are applied to goods displayed for sale in a retail store. When someone who has shoplifted one or more of such goods walks through an entrance or exit of the store, they can immediately be detected by a detector installed at the entrance and exit.
- the detectable elements for such crime-prevention use are required to be extremely small in size since they as attached to goods should go unnoticed.
- the small-size detectable elements generally produce a relatively weak magnetic field. Products of iron which are normally present around us retain some degree of residual magnetism. The detector therefore frequently fails to tell goods to which the detectable elements are attached clearly from those products of iron with such residual magnetism which happen to approach or pass by the detector. External magnetic noise generated by nearby vehicles also seriously affects the detector, which then becomes unable to detect detectable elements properly.
- Another object of the present invention is to provide a detectable element which can be detected at a relatively long distance without being seriously affected by external magnetic noise.
- a detectable element comprises a permanent magnet and means for mounting the permanent magnet on an object to be detected for its presence or passage, the permanent magnet being rotatably and vibratably supported by the mounting means.
- the mounting means may, for example, comprise a capsule housing therein the permanent magnet, which may be in the form of a ball.
- the internal volume of the capsule is greater than the volume of the permanent magnet so that the permanent magnet can freely rotate or vibrate within the capsule.
- the detectable element is attached to the object to be detected.
- a space in which detection should be carried out is filled with an alternating magnetic field by a first magnetic field generating means. When the object bearing the detectable element is in the space or passes through the space, the permanent magnet is moved under the alternating magnetic field to generate a magnetic wave.
- the magnetic wave thus generated is detected by a magnetic field sensor, which provides an output to drive a visible or audible indicator to announce the presence or passage of the object.
- a second magnetic field generating means should preferably be added to produce an auxiliary alternating magnetic field in synchronism with the first magnetic field generating means for cancelling out the alternating magnetic field present at the magnetic field sensor.
- a filter is included for picking up only signal components from the magnetic field sensor while removing noise components.
- the detectable element may be constructed to produce a sound when the permanent magnet is moved in response to the alternating magnetic field applied, and the sound generated may be picked up by a microphone which then produces an output for driving the indicator.
- a detectable element includes a permanent magnet 101 housed in a nonmagnetic capsule 102 as of synthetic resin in the shape of a hollow box with a space 103 left between the permanent magnet 101 and the walls of the capsule 102.
- the permanent magnet 101 is in the form of a ball having a diameter of about 3 mm, and is rotatable and vibratable within the capsule 102 which has an internal volume of 5 x 5 x 5 mm3, for example.
- the permanent magnet 101 is magnetized such that its lefthand half is of a north-seeking pole while the righthand half is of a south-seeking pole.
- the detectable element 101 is attached to an object to be detected.
- the permanent magnet 101 When the object enters a space in which an alternating magnetic field having a frequency f is produced, the permanent magnet 101 is driven by such an alternating magnetic field to rotate or vibrate.
- the frequehcy f is 50 Hz
- the permanent magnet 101 rotates or vibrates in synchronism with the alternating magnetic field at a frequency of f/2, f/3, or f/4.
- the permanent magnet 101 thus moves, it produces a magnetic wave having such a frequency or a frequency close thereto.
- the permanent magnet 101 rotates or vibrates at a frequency which is not equal to the frequency f but to the frequency of f/2, f/3 or f/an integral number, because of inertia of the permanent magnet 101 due to its mass or friction thereof with the capsule 102 due to its vibration.
- the magnetic wave that the permanent magnet 101 produces upon rotation or vibration is detected by a known high-sensitivity magnetic field sensor. It is experimentally determined that disturbance magnetic waves caused by iron products or vehicles passing by the magnetic field sensor generally have a frequency on the order of or below 1 Hz. Therefore, the magnetic field sensor can easily differentiate magnetic waves the permanent magnet 101 generates in the ranges of frequencies related to the frequency f from such disturbance magnetic waves.
- FIG. 4 shows a detector device for detecting the passage or presence of the magnetically detectable element as described above.
- the detector device includes a high-sensitivity magnetic field sensor 401 which may comprise a fluxgate magnetometer, a proton-precision magnetometer, a magnetic multi-type magnetometer, an SQUID magnetometer, an optical pumping magnetometer, a magnetometer having a stationary solenoid coil, a magnetometer having a rotating or vibrating magnetic path or coil, or a magnetic-flux- density sensor such as a Hall-effect device, a magnetoresistive device or a magnetic diode.
- the detector device has a coil 403 located in the vicinity of a location 402 for detecting the passage of an object that carries the detectable element as illustrated in FIG. 1.
- the coil 403 is supplied with an alternating current of a frequency of f from an AC power supply 404 to generate an alternating magnetic field of the frequency f in a space around the location 402.
- the permanent magnet 101 is actuated as described above due to the alternating magnetic field produced by the-coil 403 to thereby create magnetic waves having a frequency of f/2, f/3, f/4 or f/an integer, or a frequency close thereto.
- the magnetic field sensor 401 detects such magnetic waves and converts them into an electric signal.
- the magnetic field sensor 401 is also subjected to an alternating magnetic field having the frequency f which is produced by the current.of the frequency f flowing through the coil 403.
- an auxiliary coil 406 is disposed adjacent to the magnetic field sensor 401.
- the auxiliary coil 406 is supplied with an alternating current of a frequency f trom a power supply 407 to produce an alternating magnetic field.
- the location and shape of the auxiliary coil 406, and the magnitude of the current supplied thereto are selected such that the magnetic field generated by the coil 403 and existing at the sensor 401 will be cancelled out by the magnetic field produced by the auxiliary coil 406.
- the auxiliary coil 406 may be positioned closely to the sensor 401, or wound around the sensor 401 to allow the magnetic field from the auxiliary coil 406 to act intensively on the sensor 401 but fail to significantly affect other parts of the detector device. As a result, the alternating magnetic field of the frequency f at the location 402 comes substantially solely from the coil 403.
- the sensor 401 is subjected to the magnetic field caused by the permanent magnet 101 in a frequency range having the frequencies f/2, f/3 and the like, the disturbance magnetic field mainly of the frequencies around 1 Hz, and the earth magnetic field.
- the amplifier 405 is connected at its output with a filter 408 having frequency characteristics selected to allow passage only of signal components of the above frequency range, but reject signal components due to the disturbance magnetic field and the DC magnetic field.
- the filter 408 produces an output signal which energizes an indicator 409 for producing a visible or audible output.
- the detector device shown in F IG. 4 can detect the passage or presence of the object with the detectable element of FIG. 1 at the location 402 without being adversely affected by the disturbance magnetic field and the earth magnetic field which act on the detector device.
- the amplifier 405 may be followed by a known notch filter 410 as shown by the dotted line in FIG. 4 for rejecting a signal having the frequency f.
- a notch filter 410 serves to compensate for any degree of failure for the auxiliary coil 406 to cancel out the magnetic field generated by the coil 403.
- the saturation level of the sensor 401 and the amplifier 405 is sufficiently high, only the notch filter 410 suffices and the auxiliary coil 406 and its power supply 407 may be dispensed with.
- the central axis of the coil 403 is shown as extending in orthogonal relation to the central axis of the auxiliary coil 406 and sensor 401, these central axes may extend parallel to each other or at an angle to each other.
- the detector device may include a plurality of coils 403.
- a ball-shaped permanent magnet 101 has four magnetic pcles angularly spaced at 90-degree intervals around the center of the permanent magnet 101.
- the permanent magnet 101 nay be magnetized to have more magnetic poles than four magnetic poles.
- FIG. 6 illustrates a spherical permanent magnet 101 having two diametrically opposite magnetic poles and a pair of projections 601, 602-positioned in diametrically opposite relation between the magnetic poles and serv,ig as a rotational shaft about which the spherical permament magnet 101 is rotatable within the capsule 102 as show in FIG. 1.
- the permanent magnet 101 with such projections 601, 602 may also be provided with a multiplicity of magnetic poles more than two magnetic poles. Where more than two magnetic poles are present, the magnetic wave generated by the permanent magnet 101 has a higher frequency, and the filter 408 is required to have a corresponding frequency band to pass such a higher frequency.
- FIG. 7 shows a detectable element according to still another embodiment, in which a box-shaped capsule 102 containing therein the permanent magnet 101 as shown in FIG. 1 has on one side thereof an adhesive layer 104 and a peelable layer 105 attached to an outer surface of the adhesive layer 104.
- the peelable layer 105 is first peeled off, and then the adhesive layer 104 is pressed against the object.
- the adhesive layer 104 should preferably be attached to a cover 106 through which the permanent magnet 101 can be brought into the capsule 102.
- the capsule 102 is fabricated of a box-shaped member with one side open and such a cover 106 with the adhesive layer 104 and peelable layer 105 placed thereon, the cover 106 being bonded, fused or otherwise fixed to the box-shaped member.
- the cover 106 can be prepared in quantities by being cut out of a sheet having adhesive and peelable layers mounted thereon.
- a capsule 102 may be in the shape of a hat including a flange 107 with an adhesive layer 104 and a peelable layer 105 thereon.
- the peelable layer 105 is peeled and the adhesive layer 104 is stuck to the object.
- the permanent magnet 101 is disposed in a space defined between the hat-shaped capsule 102 and the object.
- a cover 106 is attached to a hat-shaped capsule 102 and supports thereon an adhesive layer 104 and a peelable layer 105.
- a capsule 102 is made of a flexible material and has a constricted opening 108 having a diameter which is slightly smaller than that of the permanent magnet 101.
- the permanent magnet 101 is forcibly pushed into the capsule 102 through the opening 108.
- the capsule 102 has a flange 107 on which an adhesive layer 104 is placed.
- a capsule 102 shown in FIG. 11 comprises a plate 110 having a cylindrical through hole 109 and a pair of covers 111, 112 closing the through hole 109, the plate 110 being square, circular, or of other desired shapes.
- FIG. 12 shows still another capsule composed of a plate 110 having a bottomed hole 113 containing the permanent magnet and a cover 112 by which the bottomed hole 113 is closed.
- the detectable elements as illustrated in FIGS. 11 and 12 can serve as price tags with prices printed thereon.
- a detectable element may be bonded to a sheet-like object such as a price tag, a card, a label, or a decal, and such a sheet-like object may then be attached to other objects such as goods for sale.
- the sheet-like object may be attached by either being directly applied to the other objects or by applying the detectable element 30 to such objects.
- a detectable element 30 may be fixedly mounted in a package 21 for containing an article for sale, or a detectable element 30' may be attached to an outer surface of the package 21, or a detectable element 30" may be embedded in the package 21.
- a detectable element 102 is formed as an integral part of a thin object 40 such as a sheet, a film, or a plate.
- the permanent magnet 101 is not limited to a spherical shape, but may be in the form of a plate, a polyhedral body, or in any other desired shapes.
- the permanent magnet 101 may be flexible.
- the flexible permanent magnet 101 as shown in FIG. 16 is plate- or rod-shaped and has one end 101a fixed to an object 50 the passage or presence of which should be detected.
- the flexible permanent magnet 101 may comprise a rubber magnet, a plastic magnet, or a paper magnet, for instance.
- the free end of the permanent magnet 101 is vibratable when placed in an alternating magnetic field.
- the permanent magnet 101 may not necessarily be housed in the capsule 102.
- a permanent magnet 101 has a through hole 115 extending diametrically between the north-seeking and south-seeking poles.
- the permanent magnet 101 with such a through hole 115 may be in other solid shapes than the sphere,.and may be magnetized to have a multiplicity of magnetic poles.
- a thread (not shovm) will extend through the through hole 115 for connecting the permanent magnet 101 to an object to be detected for its passage or presence.
- a solid permanent magnet 101 which may be in any desired shapes may be tied or bonded to a thread, which is connected to an object to be detected. The permanent magnet thus attached to the object is movable when put in an alternating magnetic field.
- the permanent magnet 101 of various forms may not be housed in the capsule 102, but may be accommodated in a cavity in an object to be-detected so that the permanent magnet 101 can be moved in the cavity.
- a magnetic wave emanating from the permanent magnet 101 as it moves under an alternating magnetic field is picked up to detect an object to which the permanent magnet is attached.
- an arrangement may be made to detect a sound generated upon movement of the permanent magnet 101 with a microphone.
- the capsule 102 as shown in FIGS. 1 and 2 is made of nonmagnetic material such as copper, brass, aluminum, or porcelain, and a sound produced when the permanent magnet 101 collides with the capsule 102 due to rotary or vibratory motion under an alternating magnetic field applied can be picked up by a microphone for detecting the passage or presence of the detectable element.
- FIG. 18 shows one such application in which a capsule 102 and a permanent magnet 101 jointly constitute a bell having a ring 121 through which extends a thread (not shown) attached to an object to be detected.
- the capsule 102 When the permanent magnet 101 hits the capsule 102, the capsule 102 emits a resonant sound which is relatively large in intensity.
- a bar-shaped vibrator or sound-producing body 116 has one end fixed to a support 117 and supports a permanent magnet 101 on its free end.
- the sound-producing body 116 When the permanent magnet 101 vibrates under an alternating magnetic field applied, the sound-producing body 116 generates a sound for detecting an object with which such a detectable element is associated.
- a sound-producing body may itself be comprised of a permanent magnet 101.
- a sound-producing body 116 is housed in a capsule 102 with one end supported thereon, and a permanent magnet 101 is movably accommodated in the capsule 102. When the permanent magnet 101 is moved in the capsule 102 under an alternating magnetic field applied, the permanent magnet 101 collides with the sound-producing body 116.
- the sound thus produced can be picked up by a microphone 411 which then generates an output that is amplified by an amplifier 405.
- An output signal from the amplifier 405 is processed by a filter 412 so as to remove noise signal components.
- the filter 412 supplies its output to an indicator 409. Where the sound-producing body 116 comprises a vibrator, the filter 412 passes only a signal having a frequency at which the vibrator vibrates.
- the detectable element according to the present invention can be attached to an object or a human body to be detected.
- the detectable element can reliably be detected even at a relatively long distance without being seriously affected by external magnetic noises or residual magnetism in products of iron.
- the permanent magnet 101 in the form of a ball is small in size, about 3 mm across, and inexpensive to fabricate. Therefore, the detectable element is less costly to construct.
- the detectable element or an object to which it is attached may be processed by a demagnetizer used as for magnetic recording tapes to demagnetize the. permanent magnet 101 with ease.
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Abstract
Description
- The present invention relates to a detectable element for enabling a detector to detect the passage or presence of an object to which the detectable element is attached.
- There has been proposed a detectable element which comprises a small permanent magnet that can be attached to an object to be detected. When the object with such a permanent magnet attached reaches a certain location, the magnetic flux emanating from the permanent magnet is detected by a detector so that arrival of the object at the location or passage thereof through the location can be ascertained. Such detectable elements have found a wide variety of applications. For example, the detectable elements are applied to goods displayed for sale in a retail store. When someone who has shoplifted one or more of such goods walks through an entrance or exit of the store, they can immediately be detected by a detector installed at the entrance and exit.
- The detectable elements for such crime-prevention use are required to be extremely small in size since they as attached to goods should go unnoticed. The small-size detectable elements generally produce a relatively weak magnetic field. Products of iron which are normally present around us retain some degree of residual magnetism. The detector therefore frequently fails to tell goods to which the detectable elements are attached clearly from those products of iron with such residual magnetism which happen to approach or pass by the detector. External magnetic noise generated by nearby vehicles also seriously affects the detector, which then becomes unable to detect detectable elements properly.
- It is an object of the present invention to provide a detectable element which is small in size, less costly to construct, and can reliably detected.
- Another object of the present invention is to provide a detectable element which can be detected at a relatively long distance without being seriously affected by external magnetic noise.
- According to the present invention, a detectable element comprises a permanent magnet and means for mounting the permanent magnet on an object to be detected for its presence or passage, the permanent magnet being rotatably and vibratably supported by the mounting means. The mounting means may, for example, comprise a capsule housing therein the permanent magnet, which may be in the form of a ball. The internal volume of the capsule is greater than the volume of the permanent magnet so that the permanent magnet can freely rotate or vibrate within the capsule. The detectable element is attached to the object to be detected. A space in which detection should be carried out is filled with an alternating magnetic field by a first magnetic field generating means. When the object bearing the detectable element is in the space or passes through the space, the permanent magnet is moved under the alternating magnetic field to generate a magnetic wave. The magnetic wave thus generated is detected by a magnetic field sensor, which provides an output to drive a visible or audible indicator to announce the presence or passage of the object. A second magnetic field generating means should preferably be added to produce an auxiliary alternating magnetic field in synchronism with the first magnetic field generating means for cancelling out the alternating magnetic field present at the magnetic field sensor. A filter is included for picking up only signal components from the magnetic field sensor while removing noise components. The detectable element may be constructed to produce a sound when the permanent magnet is moved in response to the alternating magnetic field applied, and the sound generated may be picked up by a microphone which then produces an output for driving the indicator.
- The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which certain preferred embodiments of the present invention are shown by way of illustrative example.
-
- FIG. 1 is a perspective view of a detectable element according to the present invention;
- FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;
- FIG. 3 is a front elevational view of a permanent magnet incorporated in the detectable element shown in FIG. 1;
- FIG. 4 is a block diagram of a circuit for magnetically detecting the detecting element of the present invention;
- FIG. 5 is a front elevational view of a permanent magnet having four magnetic poles;
- FIG. 6 is a front elevational view of a permanent magnet having a pair of projections jointly serving as a rotational shaft;
- FIG. 7 is a cross-sectional view of a detectable element having an adhesive layer;
- FIG. 8 is a cross-sectional view of a detectable element having a hat-shaped capsule;
- FIG. 9 is a cross-sectional view of a detectable element which is a modification of the detectable element shown in FIG. 8;
- FIG. 10 is a cross-sectional view of a detectable element having a pot-shaped capsule;
- FIG. 11 is a cross-sectional view of a detectable element having a plate-shaped capsule;
- FIG. 12 is a cross-sectional view of a detectable element having another plate-shaped capsule;
- FIG. 13 is a perspective view of a detectable element as attached to a plate-like object;
- FIG. 14 is a cross-sectional view showing various positions in which the detectable element of the invention can be attached to a package container;
- FIG. 15 is a perspective view of a detectable element as applied to a sheet-like object;
- FIG. 16 is a front elevational view of a detectable element incorporating a flexible permanent magnet;
- FIG. 17 is a front elevational view of a permanent magnet having a mounting hole;
- FIG. 18 is a front elevational view of a detectable element constructed as part of a bell;
- FIG. 19 is a perspective view of a detectable element as attached to a sound-producing body;
- FIG. 20 is a cross-sectional view of a permanent magnet doubling as a sound-producing body;
- FIG. 21 is a perspective view of a detectable element as combined with a sound-producing body; and
- FIG. 22 is a block diagram of a circuit for detecting a sound given off by a detectable element.
- As shown in FIGS. 1 and 2, a detectable element according to an embodiment of the present invention includes a
permanent magnet 101 housed in anonmagnetic capsule 102 as of synthetic resin in the shape of a hollow box with aspace 103 left between thepermanent magnet 101 and the walls of thecapsule 102. Thepermanent magnet 101 is in the form of a ball having a diameter of about 3 mm, and is rotatable and vibratable within thecapsule 102 which has an internal volume of 5 x 5 x 5 mm3, for example. As shown in FIG. 3, thepermanent magnet 101 is magnetized such that its lefthand half is of a north-seeking pole while the righthand half is of a south-seeking pole. Thedetectable element 101 is attached to an object to be detected. When the object enters a space in which an alternating magnetic field having a frequency f is produced, thepermanent magnet 101 is driven by such an alternating magnetic field to rotate or vibrate. Experiments indicate that where the frequehcy f is 50 Hz, thepermanent magnet 101 rotates or vibrates in synchronism with the alternating magnetic field at a frequency of f/2, f/3, or f/4. When thepermanent magnet 101 thus moves, it produces a magnetic wave having such a frequency or a frequency close thereto. When the frequency f is higher than a certain frequency, then thepermanent magnet 101 rotates or vibrates at a frequency which is not equal to the frequency f but to the frequency of f/2, f/3 or f/an integral number, because of inertia of thepermanent magnet 101 due to its mass or friction thereof with thecapsule 102 due to its vibration. The magnetic wave that thepermanent magnet 101 produces upon rotation or vibration is detected by a known high-sensitivity magnetic field sensor. It is experimentally determined that disturbance magnetic waves caused by iron products or vehicles passing by the magnetic field sensor generally have a frequency on the order of or below 1 Hz. Therefore, the magnetic field sensor can easily differentiate magnetic waves thepermanent magnet 101 generates in the ranges of frequencies related to the frequency f from such disturbance magnetic waves. - FIG. 4 shows a detector device for detecting the passage or presence of the magnetically detectable element as described above. The detector device includes a high-sensitivity
magnetic field sensor 401 which may comprise a fluxgate magnetometer, a proton-precision magnetometer, a magnetic multi-type magnetometer, an SQUID magnetometer, an optical pumping magnetometer, a magnetometer having a stationary solenoid coil, a magnetometer having a rotating or vibrating magnetic path or coil, or a magnetic-flux- density sensor such as a Hall-effect device, a magnetoresistive device or a magnetic diode. The detector device has acoil 403 located in the vicinity of alocation 402 for detecting the passage of an object that carries the detectable element as illustrated in FIG. 1. Thecoil 403 is supplied with an alternating current of a frequency of f from anAC power supply 404 to generate an alternating magnetic field of the frequency f in a space around thelocation 402. When the object with the detectable element passes through thelocation 402, thepermanent magnet 101 is actuated as described above due to the alternating magnetic field produced by the-coil 403 to thereby create magnetic waves having a frequency of f/2, f/3, f/4 or f/an integer, or a frequency close thereto. Themagnetic field sensor 401 detects such magnetic waves and converts them into an electric signal. Themagnetic field sensor 401 is also subjected to an alternating magnetic field having the frequency f which is produced by the current.of the frequency f flowing through thecoil 403. Since such an alternating magnetic field is quite intensive as compared with the magnetic field generated by the motion of thepermanent magnet 101, themagnetic field sensor 401 or anamplifier 405 for amplifying an output therefrom tends to be saturated, resulting in a measurement failure. To cope with this difficulty, anauxiliary coil 406 is disposed adjacent to themagnetic field sensor 401. Theauxiliary coil 406 is supplied with an alternating current of a frequency f trom apower supply 407 to produce an alternating magnetic field. The location and shape of theauxiliary coil 406, and the magnitude of the current supplied thereto are selected such that the magnetic field generated by thecoil 403 and existing at thesensor 401 will be cancelled out by the magnetic field produced by theauxiliary coil 406. Theauxiliary coil 406 may be positioned closely to thesensor 401, or wound around thesensor 401 to allow the magnetic field from theauxiliary coil 406 to act intensively on thesensor 401 but fail to significantly affect other parts of the detector device. As a result, the alternating magnetic field of the frequency f at thelocation 402 comes substantially solely from thecoil 403. - The
sensor 401 is subjected to the magnetic field caused by thepermanent magnet 101 in a frequency range having the frequencies f/2, f/3 and the like, the disturbance magnetic field mainly of the frequencies around 1 Hz, and the earth magnetic field. Theamplifier 405 is connected at its output with afilter 408 having frequency characteristics selected to allow passage only of signal components of the above frequency range, but reject signal components due to the disturbance magnetic field and the DC magnetic field. Thefilter 408 produces an output signal which energizes anindicator 409 for producing a visible or audible output. Thus, the detector device shown in FIG. 4 can detect the passage or presence of the object with the detectable element of FIG. 1 at thelocation 402 without being adversely affected by the disturbance magnetic field and the earth magnetic field which act on the detector device. Theamplifier 405 may be followed by a knownnotch filter 410 as shown by the dotted line in FIG. 4 for rejecting a signal having the frequency f. Such anotch filter 410 serves to compensate for any degree of failure for theauxiliary coil 406 to cancel out the magnetic field generated by thecoil 403. Where the saturation level of thesensor 401 and theamplifier 405 is sufficiently high, only thenotch filter 410 suffices and theauxiliary coil 406 and itspower supply 407 may be dispensed with. While the central axis of thecoil 403 is shown as extending in orthogonal relation to the central axis of theauxiliary coil 406 andsensor 401, these central axes may extend parallel to each other or at an angle to each other. The detector device may include a plurality ofcoils 403. - As shown in FIG. 5, a ball-shaped
permanent magnet 101 according to another embodiment has four magnetic pcles angularly spaced at 90-degree intervals around the center of thepermanent magnet 101. Thepermanent magnet 101 nay be magnetized to have more magnetic poles than four magnetic poles. FIG. 6 illustrates a sphericalpermanent magnet 101 having two diametrically opposite magnetic poles and a pair ofprojections 601, 602-positioned in diametrically opposite relation between the magnetic poles and serv,ig as a rotational shaft about which the sphericalpermament magnet 101 is rotatable within thecapsule 102 as show in FIG. 1. Thepermanent magnet 101 withsuch projections permanent magnet 101 has a higher frequency, and thefilter 408 is required to have a corresponding frequency band to pass such a higher frequency. - FIG. 7 shows a detectable element according to still another embodiment, in which a box-shaped
capsule 102 containing therein thepermanent magnet 101 as shown in FIG. 1 has on one side thereof anadhesive layer 104 and apeelable layer 105 attached to an outer surface of theadhesive layer 104. When the detectable element is to be applied to an object, thepeelable layer 105 is first peeled off, and then theadhesive layer 104 is pressed against the object. Theadhesive layer 104 should preferably be attached to acover 106 through which thepermanent magnet 101 can be brought into thecapsule 102. Thecapsule 102 is fabricated of a box-shaped member with one side open and such acover 106 with theadhesive layer 104 andpeelable layer 105 placed thereon, thecover 106 being bonded, fused or otherwise fixed to the box-shaped member. Thecover 106 can be prepared in quantities by being cut out of a sheet having adhesive and peelable layers mounted thereon. - As illustrated in FIG. 8, a
capsule 102 may be in the shape of a hat including aflange 107 with anadhesive layer 104 and apeelable layer 105 thereon. For attachment to an object, thepeelable layer 105 is peeled and theadhesive layer 104 is stuck to the object. Thepermanent magnet 101 is disposed in a space defined between the hat-shapedcapsule 102 and the object. According to an embodiment shown in FIG. 9, acover 106 is attached to a hat-shapedcapsule 102 and supports thereon anadhesive layer 104 and apeelable layer 105. In FIG. 10, acapsule 102 is made of a flexible material and has a constrictedopening 108 having a diameter which is slightly smaller than that of thepermanent magnet 101. Thepermanent magnet 101 is forcibly pushed into thecapsule 102 through theopening 108. Thecapsule 102 has aflange 107 on which anadhesive layer 104 is placed. - A
capsule 102 shown in FIG. 11 comprises aplate 110 having a cylindrical throughhole 109 and a pair ofcovers hole 109, theplate 110 being square, circular, or of other desired shapes. FIG. 12 shows still another capsule composed of aplate 110 having a bottomedhole 113 containing the permanent magnet and acover 112 by which the bottomedhole 113 is closed. The detectable elements as illustrated in FIGS. 11 and 12 can serve as price tags with prices printed thereon. - The detectable elements as described above are in most cases attached to objects. As shown in FIG. 13, however, a detectable element may be bonded to a sheet-like object such as a price tag, a card, a label, or a decal, and such a sheet-like object may then be attached to other objects such as goods for sale. The sheet-like object may be attached by either being directly applied to the other objects or by applying the
detectable element 30 to such objects. As shown in FIG. 14, adetectable element 30 may be fixedly mounted in apackage 21 for containing an article for sale, or a detectable element 30' may be attached to an outer surface of thepackage 21, or adetectable element 30" may be embedded in thepackage 21. In FIG. 15, adetectable element 102 is formed as an integral part of athin object 40 such as a sheet, a film, or a plate. - The
permanent magnet 101 is not limited to a spherical shape, but may be in the form of a plate, a polyhedral body, or in any other desired shapes. In addition, thepermanent magnet 101 may be flexible. The flexiblepermanent magnet 101 as shown in FIG. 16 is plate- or rod-shaped and has oneend 101a fixed to anobject 50 the passage or presence of which should be detected. The flexiblepermanent magnet 101 may comprise a rubber magnet, a plastic magnet, or a paper magnet, for instance. The free end of thepermanent magnet 101 is vibratable when placed in an alternating magnetic field. - The
permanent magnet 101 may not necessarily be housed in thecapsule 102. For example, as shown in FIG. 17, apermanent magnet 101 has a throughhole 115 extending diametrically between the north-seeking and south-seeking poles. Thepermanent magnet 101 with such a throughhole 115 may be in other solid shapes than the sphere,.and may be magnetized to have a multiplicity of magnetic poles. A thread (not shovm) will extend through the throughhole 115 for connecting thepermanent magnet 101 to an object to be detected for its passage or presence. Although not shown, a solidpermanent magnet 101 which may be in any desired shapes may be tied or bonded to a thread, which is connected to an object to be detected. The permanent magnet thus attached to the object is movable when put in an alternating magnetic field. - The
permanent magnet 101 of various forms may not be housed in thecapsule 102, but may be accommodated in a cavity in an object to be-detected so that thepermanent magnet 101 can be moved in the cavity. - In the foregoing embodiments, a magnetic wave emanating from the
permanent magnet 101 as it moves under an alternating magnetic field is picked up to detect an object to which the permanent magnet is attached. However, an arrangement may be made to detect a sound generated upon movement of thepermanent magnet 101 with a microphone. For example, thecapsule 102 as shown in FIGS. 1 and 2 is made of nonmagnetic material such as copper, brass, aluminum, or porcelain, and a sound produced when thepermanent magnet 101 collides with thecapsule 102 due to rotary or vibratory motion under an alternating magnetic field applied can be picked up by a microphone for detecting the passage or presence of the detectable element. - FIG. 18 shows one such application in which a
capsule 102 and apermanent magnet 101 jointly constitute a bell having aring 121 through which extends a thread (not shown) attached to an object to be detected. When thepermanent magnet 101 hits thecapsule 102, thecapsule 102 emits a resonant sound which is relatively large in intensity. - As shown in FIG. 19, a bar-shaped vibrator or sound-producing
body 116 has one end fixed to asupport 117 and supports apermanent magnet 101 on its free end. When thepermanent magnet 101 vibrates under an alternating magnetic field applied, the sound-producingbody 116 generates a sound for detecting an object with which such a detectable element is associated. In FIG. 20, a sound-producing body may itself be comprised of apermanent magnet 101. According to a still further embodiment as shown in FIG. 21, a sound-producingbody 116 is housed in acapsule 102 with one end supported thereon, and apermanent magnet 101 is movably accommodated in thecapsule 102. When thepermanent magnet 101 is moved in thecapsule 102 under an alternating magnetic field applied, thepermanent magnet 101 collides with the sound-producingbody 116. - As shown in FIG. 22, the sound thus produced can be picked up by a
microphone 411 which then generates an output that is amplified by anamplifier 405. An output signal from theamplifier 405 is processed by afilter 412 so as to remove noise signal components. Thefilter 412 supplies its output to anindicator 409. Where the sound-producingbody 116 comprises a vibrator, thefilter 412 passes only a signal having a frequency at which the vibrator vibrates. - The detectable element according to the present invention can be attached to an object or a human body to be detected. When the object or human body carrying the detectable element enters a space filled with an alternating magnetic field, the detectable element can reliably be detected even at a relatively long distance without being seriously affected by external magnetic noises or residual magnetism in products of iron. The
permanent magnet 101 in the form of a ball is small in size, about 3 mm across, and inexpensive to fabricate. Therefore, the detectable element is less costly to construct. The detectable element or an object to which it is attached may be processed by a demagnetizer used as for magnetic recording tapes to demagnetize the.permanent magnet 101 with ease. - Although certain preferred embodiments have been shown and described, it should be understood that many changes and modifications may be made therein without departing from the scope of the appended claims.
Claims (22)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP129514/81 | 1981-08-18 | ||
JP56129514A JPS5830688A (en) | 1981-08-18 | 1981-08-18 | Sensor |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0072552A2 true EP0072552A2 (en) | 1983-02-23 |
EP0072552A3 EP0072552A3 (en) | 1983-08-03 |
EP0072552B1 EP0072552B1 (en) | 1986-03-12 |
Family
ID=15011372
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP82107389A Expired EP0072552B1 (en) | 1981-08-18 | 1982-08-13 | Detectable element |
Country Status (4)
Country | Link |
---|---|
US (1) | US4527153A (en) |
EP (1) | EP0072552B1 (en) |
JP (1) | JPS5830688A (en) |
DE (1) | DE3269828D1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2639743A1 (en) * | 1988-11-25 | 1990-06-01 | Gall Rita | Anti-theft device to be pressed onto smooth and rigid surfaces by a sucker |
US9652956B2 (en) | 2013-05-14 | 2017-05-16 | Alert Systems Aps | Theft-preventing system and method with magnetic field detection |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07112493B2 (en) * | 1986-07-15 | 1995-12-06 | シ−メンス、アクチエンゲゼルシヤフト | A pacemaker implanted in a patient to stimulate the patient's heart |
US4884067A (en) * | 1987-08-13 | 1989-11-28 | Talkie Tooter (Canada) Ltd. | Motion and position sensing alarm |
US5118398A (en) * | 1989-12-05 | 1992-06-02 | United Technologies Corporation | Method and an apparatus for detecting ionizable substance |
GB9722938D0 (en) * | 1997-10-30 | 1998-01-07 | Flying Null Ltd | Generating magnetic fields |
JP2002042078A (en) * | 2000-07-21 | 2002-02-08 | Leading Information Technology Institute | Electronic tag device |
US6784796B2 (en) | 1999-12-17 | 2004-08-31 | The Regents Of The University Of Califronia | Magnetic vector field tag and seal |
AU6630101A (en) * | 2000-06-22 | 2002-01-02 | Kol Medical Ltd. | Chest piece for stethoscopes, and methods of utilizing stethoscopes for monitoring the physiological conditons of patient |
US6646555B1 (en) | 2000-07-18 | 2003-11-11 | Marconi Communications Inc. | Wireless communication device attachment and detachment device and method |
FR2842744B1 (en) * | 2002-07-24 | 2006-06-30 | Michel Desroses | DEVICE FOR DETECTING THE NATURE OF A COUP AND FOR MEASURING ITS STRENGTH, METHOD FOR IMPLEMENTING THE SAME AND ITS APPLICATION TO THE ARBITRATION OF A SPORT |
US6981420B2 (en) * | 2003-12-01 | 2006-01-03 | Lowrance Arlen J | Omni-directional movement sensor |
CN101282677B (en) * | 2005-10-05 | 2010-07-28 | 奥林巴斯医疗株式会社 | Capsule type medical device, its guidance system and guidance method and examinee insertion device |
FR2898717A1 (en) * | 2006-03-27 | 2007-09-21 | Michel Desroses | Stroke`s e.g. impact, presence detecting and force measuring device for refereeing e.g. taekwondo sports, has sensors including respective capacitor and inductor that is integrated to body associated with target while moving |
US9410823B2 (en) | 2012-07-13 | 2016-08-09 | Qualcomm Incorporated | Systems, methods, and apparatus for detection of metal objects in a predetermined space |
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US3577136A (en) * | 1967-08-04 | 1971-05-04 | Security Systems Inc | Short-range signaling system |
US3611345A (en) * | 1969-04-16 | 1971-10-05 | Intron Int Inc | Motion detector |
DE2430710A1 (en) * | 1974-06-26 | 1976-01-15 | Honeywell Gmbh | Positioner change sensor - responds to rotation about at least one axis and protects objects against unauthorised removal |
US4074249A (en) * | 1977-02-04 | 1978-02-14 | Knogo Corporation | Magnetic detection means |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3754225A (en) * | 1971-06-03 | 1973-08-21 | Reaction Instr Inc | Portable equipment security system |
-
1981
- 1981-08-18 JP JP56129514A patent/JPS5830688A/en active Pending
-
1982
- 1982-07-26 US US06/402,013 patent/US4527153A/en not_active Expired - Lifetime
- 1982-08-13 DE DE8282107389T patent/DE3269828D1/en not_active Expired
- 1982-08-13 EP EP82107389A patent/EP0072552B1/en not_active Expired
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3577136A (en) * | 1967-08-04 | 1971-05-04 | Security Systems Inc | Short-range signaling system |
US3611345A (en) * | 1969-04-16 | 1971-10-05 | Intron Int Inc | Motion detector |
DE2430710A1 (en) * | 1974-06-26 | 1976-01-15 | Honeywell Gmbh | Positioner change sensor - responds to rotation about at least one axis and protects objects against unauthorised removal |
US4074249A (en) * | 1977-02-04 | 1978-02-14 | Knogo Corporation | Magnetic detection means |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2639743A1 (en) * | 1988-11-25 | 1990-06-01 | Gall Rita | Anti-theft device to be pressed onto smooth and rigid surfaces by a sucker |
US9652956B2 (en) | 2013-05-14 | 2017-05-16 | Alert Systems Aps | Theft-preventing system and method with magnetic field detection |
Also Published As
Publication number | Publication date |
---|---|
EP0072552B1 (en) | 1986-03-12 |
DE3269828D1 (en) | 1986-04-17 |
JPS5830688A (en) | 1983-02-23 |
EP0072552A3 (en) | 1983-08-03 |
US4527153A (en) | 1985-07-02 |
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